title: Resistance to vemurafenib resulting from a novel mutation in the BRAFV600E kinase domain.
abstract: Resistance to the BRAF inhibitor vemurafenib poses a significant problem for the treatment of BRAFV600E-positive melanomas. It is therefore critical to prospectively identify all vemurafenib resistance mechanisms prior to their emergence in the clinic. The vemurafenib resistance mechanisms described to date do not result from secondary mutations within BRAFV600E. To search for possible mutations within BRAFV600E that can confer drug resistance, we developed a systematic experimental approach involving targeted saturation mutagenesis, selection of drug-resistant variants, and deep sequencing. We identified a single nucleotide substitution (T1514A, encoding L505H) that greatly increased drug resistance in cultured cells and mouse xenografts. The kinase activity of BRAFV600E/L505H was higher than that of BRAFV600E, resulting in cross-resistance to a MEK inhibitor. However, BRAFV600E/L505H was less resistant to several other BRAF inhibitors whose binding sites were further from L505 than that of PLX4720. Our results identify a novel vemurafenib-resistant mutant and provide insights into the treatment for melanomas bearing this mutation.
authors.affiliation: Howard Hughes Medical Institute, Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Wagenaar
authors.forename: Leyuan
authors.initials: L
authors.lastname: Ma
authors.forename: Benjamin
authors.initials: B
authors.lastname: Roscoe
authors.forename: Sung Mi
authors.initials: SM
authors.lastname: Park
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Bolon
authors.forename: Michael R
authors.initials: MR
authors.lastname: Green
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D064593:Heterografts; D006801:Humans; D007211:Indoles / Q000493:pharmacokinetics*; D008545:Melanoma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D020125:Mutation, Missense; D009368:Neoplasm Transplantation; D017434:Protein Structure, Tertiary; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D013449:Sulfonamides / Q000493:pharmacokinetics*; D000077484:Vemurafenib
chemical_list: D007211:Indoles; D013449:Sulfonamides; D000077484:Vemurafenib; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf
keywords: BRAFV600E; deep sequencing; drug resistance; saturation mutagenesis; vemurafenib